Numerical band gap

ABSTRACT

A system includes a bandgap temperature sensor to generate multiple base-emitter voltages. The system also include a controller to detect the base-emitter voltages generated by the bandgap temperature sensor and to generate a bandgap reference voltage according to the multiple base-emitter voltage signals, the bandgap reference voltage having a voltage level that remains substantially constant relative to environmental temperature variations.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/912,399, filed Apr. 17, 2007, which is incorporated herein byreference.

TECHNICAL FIELD

This disclosure relates generally to electronic circuits, and moreparticularly to numerical band gaps.

BACKGROUND

Many electronic circuits include analog temperature sensors to detectthe temperature of their environment. These temperature sensors oftensupply fixed currents to a pair of diodes or bipolar junctiontransistors operating with different current densities, and then comparethe associated base-emitter voltages V_(BE) to determine anenvironmental temperature. Although these conventional temperaturesensors can determine the temperature of their environment, theytypically include analog circuit elements, such as operationalamplifiers, which occupy a relatively large area on a chip and consume arelatively large amount of power.

SUMMARY

A device includes a bandgap temperature sensor to generate multiplebase-emitter voltages, and a system controller to detect thebase-emitter voltages generated by the bandgap temperature sensor and togenerate a bandgap reference voltage according to the multiplebase-emitter voltages. The bandgap reference voltage can have a voltagelevel that remains substantially constant relative to a temperatureassociated with the bandgap temperature sensor.

The system controller can determine a difference in the base-emittervoltages, and to generate the bandgap reference voltage from thedifference in the base-emitter voltages and at least one of thebase-emitter voltages. The system controller can add the difference inthe base-emitter voltages to one of the base-emitter voltages togenerate the bandgap reference voltage. The system controller canmultiply the difference in the base-emitter voltages to a constant valueand then to add the multiplied difference in the base-emitter voltagesto one of the base-emitter voltages to generate the bandgap referencevoltage. The constant value can be based at least in part oncharacteristics of the bandgap temperature sensor.

The bandgap temperature sensor includes a variable current source toprovide a first current to a transistor to generate a first base-emittervoltage signal, and to provide a second current to the transistor togenerate a second base-emitter voltage signal. The device includes ananalog-to-digital converter to convert base-emitter voltages intodigital base-emitter voltage signals, the system controller to generatethe bandgap voltage according to the digital base-emitter voltagesignals.

A method includes detecting multiple base-emitter voltages generated bya bandgap temperature sensor, and generating a bandgap reference voltageaccording to the multiple base-emitter voltage signals, the bandgapreference voltage to remain substantially constant relative toenvironmental temperature variations.

The method can also include determining a difference in the base-emittervoltages, and generating the bandgap reference voltage from thedifference in the base-emitter voltages and at least one of thebase-emitter voltages.

The generating of the bandgap reference voltage can include adding thedifference in the base-emitter voltages to one of the base-emittervoltages. The generating of the bandgap reference voltage can includemultiplying the difference in the base-emitter voltages to a constantvalue, and adding the multiplied difference in the base-emitter voltagesto one of the base-emitter voltages. The constant value can be based atleast in part on the characteristics of the bandgap temperature sensor.

The method can include generating a first base-emitter voltage signalwhen a first current signal is provided to a transistor, generating asecond base-emitter voltage signal when a second current signal isprovided to the transistor, determining a difference between the firstbase-emitter voltage signal and the second base-emitter voltage signal,and generating the bandgap reference voltage based, at least in part, onthe determined difference between the first base-emitter voltage signaland the second base-emitter voltage signal.

A system includes a memory to store computer-readable instructions, anda microprocessor to receive the instructions stored in memory, theinstructions, when executed, cause the microprocessor to identifymultiple base-emitter voltages generated by a bandgap temperaturesensor, and generate a bandgap reference voltage according to themultiple base-emitter voltage signals, where the bandgap referencevoltage having a voltage level that remains substantially constantrelative to environmental temperature variations.

The microprocessor can determine a difference in the base-emittervoltages, and generate the bandgap reference voltage from the differencein the base-emitter voltages and at least one of the base-emittervoltages. The base-emitter voltages decrease as the environmentaltemperature increases, and the difference in the base-emitter voltagesincreases as the environment temperature increases. The microprocessorcan add the difference in the base-emitter voltages to one of thebase-emitter voltages to generate the bandgap reference voltage. Themicroprocessor can multiply the difference in the base-emitter voltagesto a constant value, and add the multiplied difference in thebase-emitter voltages to one of the base-emitter voltages to generatethe bandgap reference voltage. The constant value can be based at leastin part on the characteristics of the bandgap temperature sensor.

The bandgap temperature sensor can generate a first base-emitter voltagesignal when a first current signal is provided to a transistor and togenerate a second base-emitter voltage signal when a second currentsignal is provided to the transistor. The microprocessor can determine adifference between the first base-emitter voltage signal and the secondbase-emitter voltage signal, and generate the bandgap reference voltagebased, at least in part, on the determined difference between the firstbase-emitter voltage signal and the second base-emitter voltage signal.

DESCRIPTION OF THE DRAWINGS

The invention can be best understood by reading the disclosure withreference to the drawings.

FIG. 1 is a block diagram of a bandgap voltage reference systemaccording to embodiments of the invention.

FIGS. 2 and 3 are block diagrams of embodiments of a temperature sensorshown in FIG. 1.

FIG. 4 is an example chart illustrating a relationship betweenenvironmental temperature and voltages of the bandgap voltage referencesystem shown in FIG. 1.

FIG. 5 is an example flowchart of the bandgap voltage reference systemshown in FIG. 1.

DETAILED DESCRIPTION

A bandgap voltage reference system includes a microprocessor or othercontroller to generate or numerically build a bandgap voltage referenceaccording to base-emitter voltages detected in a bandgap temperaturesensor. Due to the relationship between the base-emitter voltages and anenvironmental temperature, the bandgap voltage reference can be atemperature flat reference that remains relatively constant as theenvironmental temperature varies. Embodiments are shown and describedbelow in greater detail.

FIG. 1 is a block diagram of a bandgap voltage reference system 100according to embodiments of the invention. Referring to FIG. 1, thebandgap voltage reference system 100 includes a microcontroller 110 togenerate, numerically build, or calculate a bandgap voltage reference140 from multiple base-emitter voltages V_(BE) generated by atemperature sensor 200. The bandgap voltage reference 140 can be atemperature flat reference, for example, having a voltage level thatremains substantially constant when there are environmental temperaturevariations associated with the bandgap voltage reference system 100. Insome embodiments, the microcontroller 110 can be a processor,microprocessor, or other controller device capable of generating thebandgap voltage reference 140, or be implemented in firmware, as adiscrete set of hardware elements, state machine, or in an on boardstore, or off board store.

The temperature sensor 200 can generate multiple analog base-emittervoltages V_(BE) signals, for example, by providing one or more currentsto at least a pair of diodes having different current densities. Thetemperature sensor 200 can also generate the analog base-emitter voltageV_(BE) signals by sequentially providing one current to a bipolarjunction transistor to determine a first analog base-emitter voltageV_(BE) signal and then providing a different current to the bipolarjunction transistor to determine a second analog base-emitter voltageV_(BE) signal. Embodiments of the temperature sensor 200 will bedescribed below in greater detail.

The microcontroller 110 can detect or measure the multiple base-emittervoltage V_(BE) signals generated by the temperature sensor 200, andgenerate the bandgap voltage reference 140 according to the multiplebase-emitter voltage V_(BE) signals. For instance, the microcontroller110 can determine a difference between the multiple base-emitter voltageV_(BE) signals, e.g., calculate a differential base-emitter voltageΔV_(BE), and then add the differential base-emitter voltage ΔV_(BE) toat least one of the multiple base-emitter voltage ΔV_(BE) signals togenerate the bandgap voltage reference 140.

Since the multiple base-emitter voltage V_(BE) signals have atemperature profile where the voltage level decreases as temperatureincreases, and the differential base-emitter voltage ΔV_(BE) has atemperature profile where the voltage level increases as temperatureincreases, the microcontroller 110 can numerically build or calculate abandgap voltage reference 140 that is insensitive to environmentaltemperature fluctuations by adding the differential base-emitter voltageΔV_(BE) with at least one of the multiple base-emitter voltage V_(BE)signals. In some embodiments, the microcontroller 110 can multiply thedifferential base-emitter voltage ΔV_(BE) with a constant value K, forexample, according to the characteristics of the temperature sensor 200,prior to adding the adding the differential base-emitter voltage ΔV_(BE)with at least one of the multiple base-emitter voltage V_(BE) signals.The microcontroller 110 can characterize or calibrate the constant valueK, for example, during wafer tests or device testing. The constant valueK can be stored in a memory 150 for use by the microcontroller 110 inthe generation of the bandgap voltage reference 140.

The bandgap voltage reference system 100 includes an analog-to-digitalconverter 120 to convert the analog base-emitter voltage V_(BE) signalsinto digital base-emitter voltage V_(BE) signals and provide the digitalbase-emitter voltage V_(BE) signals to the microcontroller 110. In someembodiments, the analog-to-digital converter 120 can be a passiveconverter, thus consuming less power and chip area compared with activeconverters.

The microcontroller 110 can generate a bandgap voltage reference 140according to the digital base-emitter voltages V_(BE). Themicrocontroller 110 can generate, calculate or numerically build thebandgap voltage reference 140 by determining a differential base-emittervoltage ΔV_(BE) from the multiple digital representations ofbase-emitter voltage V_(BE) signals provided by the analog-to-digitalconverter 130, and then adding the differential base-emitter voltageΔV_(BE) to at least one of the base-emitter voltages V_(BE).

The microcontroller 110 can also utilize the differential base-emittervoltage ΔV_(BE) that it determines, and the fact that the differentialbase-emitter voltage ΔV_(BE) is proportional to an Absolute Temperature(PTAT) value, to sense an environmental temperature value. Themicrocontroller 110 can use a memory 150 or a look-up table (not shown)to determine the environmental temperature from the differentialbase-emitter voltage ΔV_(BE).

When more than two digital base-emitter voltage V_(BE) signals areprovided from the analog-to-digital converter 130, the microcontroller110 can use any number of methods to determine the differentialbase-emitter voltage ΔV_(BE). For instance, the microcontroller 110 canfind a difference from any two of the digital base-emitter voltageV_(BE) signals and utilize the difference as the differentialbase-emitter voltage ΔV_(BE). In some embodiments, the microcontroller110 can approximate the differential base-emitter voltage ΔV_(BE) fromthe digital base-emitter voltage V_(BE) signals by averaging multipledifferences of the between the digital base-emitter voltage V_(BE)signals or by selecting one of the differences, such as the mediandifference, as the differential base-emitter voltage ΔV_(BE).

The microcontroller 110 can perform operations according toinstructions, such as bandgap reference instructions 155, stored in thememory 150. The microcontroller 110 can receive the bandgap referenceinstructions 155 that, when executed, enable the microcontroller 110 tocontrol the operation of the temperature sensor 200, detect multiplebase-emitter voltage V_(BE) signals, and generate the bandgap voltagereference 140 according to the detected base-emitter voltage V_(BE)signals.

The microcontroller 110 can control operations of the temperature sensor200 and the analog-to-digital converter 120 with control signals 130.For instance, the microcontroller 110 can select the number ofbase-emitter voltage V_(BE) signals that are generated by thetemperature sensor 200 by providing control signals 130 to thetemperature sensor 200 via the analog-to-digital converter 120. In someembodiments, the analog-to-digital converter 120 can convert the controlsignals 130 from the microcontroller 110 into analog control signals 130to control the temperature sensor 200. The microcontroller 110 can alsocontrol the operation, and/or timing of the analog-to-digital converter120. Although FIG. 1 includes a temperature sensor 200, in someembodiments, any device that generates a base-emitter voltage can beused to determine the bandgap voltage reference 140.

FIGS. 2 and 3 are block diagrams of embodiments of a temperature sensorshown in FIG. 1. Referring to FIG. 2, the temperature sensor 200includes a pair of current sources 210 and 220 to provide respectivecurrents I₁ and I₀ to a corresponding pair of diodes 230 and 240. Thepair of diodes 230 and 240 can have base-emitter voltages V_(BE) thatcorrespond to the magnitude of current provided to it by the respectivecurrent sources 210 and 220. For instance, current source 210 canprovide current I₁ to diode 230 with a current density J₁, and currentsource 220 can provide current I₀ to diode 240 with a current densityJ₀. The current sources 210 and 220 can generate the respective currentsI₁ and I₀ according to a power supply voltage 250.

The diodes 230 and 240 generate base-emitter voltages responsive toreceiving the currents I₁ and I₀ from the current sources 210 and 220,respectively. The base-emitter voltages can be measured, for example, bythe microcontroller 110, at sampling nodes 270 and 280, shown as node Aand node B, respectively. The measured or sampled base-emitter voltagesfrom sampling nodes 270 and 280 can be transferred or provided to themicrocontroller 110 for use in determining the bandgap voltage reference140.

The temperature sensor 200 includes selectors 260 to selectively providethe currents I₁ and I₀ from the current sources 210 and 220 to therespective diodes 230 and 240. The selectors 260 can receive controlsignals 130 from the microcontroller 110 that prompt the selectors 260to open blocking current being provided to at least one of the diodes230 and 240, or close allowing current to reach at least one of thediodes 230 and 240. In some embodiments, the selectors 260 can bemultiplexors that select between the currents I₁ and I₀ from the currentsources 210 and 220, and another input, such as a ground voltageresponsive to the control signals 130.

Referring to FIG. 3, the temperature sensor 300 can include a variablecurrent source 310 to provide current to a transistor 330. The variablecurrent source 310 can have a plurality of fixed current sourcesI₀-I_(N) that can be coupled in a current mirror configuration. Thevariable current source 310 can include any number of fixed currentsources capable of generating any magnitude of current. The transistor330 can be a bipolar junction transistor having a base-emitter voltageV_(BE) that corresponds to the magnitude of current provided to it bythe variable current source 310.

The variable current source 310 provides current to the transistor 330,which generates an analog base-emitter voltage responsive to thecurrent. This analog base-emitter voltage is then provided to themicrocontroller 110 after conversion by analog-to-digital converter 120.The variable current source 310 can then provide another current, with adifferent magnitude, to the transistor 330, which generates anotheranalog base-emitter voltage responsive to the new current. Afterreceiving the new base-emitter voltage, the microcontroller 110 iscapable of determining the differential base-emitter voltage and thusthe environmental temperature for the system 100.

The variable current source 310 can generate and provide current to aswitch network 320. The switch network 320 can be adapted to selectivelycouple the transistor 330 to the variable current source 310, or to oneor more of the plurality of fixed current sources I₀-I_(N).

The switch network 320 can provide current from the variable currentsource 310 to the transistor 330, which generates an analog base-emittervoltage V_(BE). The analog base-emitter voltage V_(BE) can be providedto the analog-to-digital converter 120 for conversion into a digitalbase-emitter voltage V_(BE) signal. The digital base-emitter voltageV_(BE) signal can be provided to the microcontroller 110 for furtherprocessing. This process, of the variable current source 310 generatinga current that is provided to the transistor 330 via the network switch320, is then repeated with at least one different current magnitude. Thenumber of base-emitter voltage V_(BE) signals that the temperaturesensor 300 generates and the currents utilized to generate them can beprogrammable or controllable depending on the resolution and granularityrequirements for the bandgap voltage reference system 100.

In some embodiments, the one or more of the fixed current sourcesI₀-I_(N) can be selected during the generation of a first base-emittervoltage, and subsequently select one or more of the fixed currentsources I₀-I_(N) during the generation of a second or any otherbase-emitter voltage. A current ratio larger than 1 can be maintainedbetween the current utilized to generate the first base-emitter voltageand at least one of the second or subsequent base-emitter voltages. Thiscurrent ratio can ensure the temperature sensing system 100 determines alarge ΔV_(BE), and thus generates a linear variation in temperature.

The temperature sensor 300 includes a sampling node 350, shown as acombined node A/B. The microcontroller 110 can measure or sample thebase-emitter voltages at the sampling node 350 after a selected currentis provided to the transistor 330. In some embodiments, the measured orsampled base-emitter voltages from sampling node 350 can be transferredor provided to the microcontroller 110 for use in determining thebandgap voltage reference 140.

FIG. 4 is an example chart illustrating a relationship betweenenvironmental temperature and base-emitter voltages of the bandgapvoltage reference system 100 shown in FIG. 1. Referring to FIG. 4, thechart shows temperature profiles for base-emitter voltages V_(BE),differential base emitter voltages ΔV_(BE), and the bandgap referencevoltage 140. The base-emitter voltages V_(BE) generated by thetemperature sensor 200 (or 300) have a temperature profile where theirvoltage level decreases as an environmental temperature increases. Thedifferential base-emitter voltage. ΔV_(BE) has a temperature profilewith a voltage level increasing as the environmental temperatureincreases. The bandgap voltage reference 140 can be a temperature flatreference, or having a voltage level that remains substantially constantover a temperature range. In some embodiments, the microcontroller 110can generate the bandgap voltage reference 140 by adding thedifferential base-emitter voltage ΔV_(BE), or a multiple thereof, withat least one of the base-emitter voltages V_(BE).

FIG. 5 is an example flowchart of the bandgap voltage reference systemshown in FIG. 1. Referring to FIG. 5, the flowchart begins at block 510by detecting multiple base-emitter voltages V_(BE) generated by abandgap temperature sensor. In some embodiments, the band gaptemperature sensor can generate multiple analog base-emitter voltagesV_(BE), for example, by providing one or more currents to at least apair of diodes having different current densities. The temperaturesensor can also generate the analog base-emitter voltage V_(BE) signalsby sequentially providing one current to a bipolar junction transistorto determine a first analog base-emitter voltage V_(BE) signal and thenproviding a different current to the bipolar junction transistor todetermine a second analog base-emitter voltage V_(BE) signal.

In some embdoments, the microcontroller 110 can detect or measure avoltage level of the base-emitter voltages V_(BE) generated by thetemperature sensor. The detected base-emitter voltages V_(BE) can beprovided to the microcontroller 110 from the temperature sensor, forexample, via an analog-to-digital converter 120. The analog-to-digitalconverter 120 can convert the base-emitter voltages V_(BE) to digitalrepresentations of the base-emitter voltages V_(BE) and provide them tothe microcontroller 110.

The flowchart continues to block 520 and determines a difference in thebase-emitter voltages. In some embodiments, the microcontroller 110 candetermine the difference between multiple base-emitter voltages V_(BE)to generate a differential base-emitter voltage ΔV_(BE). The number ofbase-emitter voltage V_(BE) the microcontroller 110 utilizes to generatethe differential base-emitter voltage ΔV_(BE) can be variable. Forinstance, the microcontroller 110 can generate the differentialbase-emitter voltage ΔV_(BE) by determining a difference between twobase-emitter voltages V_(BE).

The flowchart continues to block 530 and multiplies the difference inthe base-emitter voltages to a constant value K. The constant value Kcan be based at least in part on the characteristics of the bandgaptemperature sensor. In some embodiments, the constant value K is around20, which can be proportional to the voltage levels of the differentialbase-emitter voltage ΔV_(BE) and base-emitter voltages V_(BE). Themicrocontroller 110 can characterize or calibrate the constant value K,for example, during wafer tests or device testing. The constant value Kcan be stored in a memory 150 for use by the microcontroller 110 in thegeneration of the bandgap voltage reference 140.

The flowchart continues to block 540 and generates a bandgap voltagereference 140 by adding the difference in the base-emitter voltagesΔV_(BE) multiplied by the constant value K to at least one of thebase-emitter voltages V_(BE). The bandgap voltage reference 140 can be atemperature flat reference, e.g., having a voltage level that remainssubstantially constant relative to environmental temperature variations.

Although FIG. 5 discloses a microcontroller 110 capable of performingthe operations in the flowchart, in some embodiments, any controller canperform one or more of the flowchart operations. In some embodiments,the controller can be a processor, microprocessor, firmware, a discreteset of hardware elements, state machine, on-board or off-board store, orother controller device capable of generating the bandgap voltagereference 140. FIG. 5 also discloses utilizing temperature sensor 200 togenerate the base-emitter voltages, however, in some embodiments, anydevice can generate the base-emitter voltages used to determine thebandgap voltage reference 140.

One of skill in the art will recognize that the concepts taught hereincan be tailored to a particular application in many other advantageousways. In particular, those skilled in the art will recognize that theillustrated embodiments are but one of many alternative implementationsthat will become apparent upon reading this disclosure.

The preceding embodiments are exemplary. Although the specification canrefer to “an”, “one”, “another”, or “some” embodiment(s) in severallocations, this does not necessarily mean that each such reference is tothe same embodiment(s), or that the feature only applies to a singleembodiment.

1. A device comprising: a bandgap temperature sensor to generatemultiple base-emitter voltages; and a system controller to detect thebase-emitter voltages generated by the bandgap temperature sensor and togenerate a bandgap reference voltage according to the multiplebase-emitter voltages, the bandgap reference voltage having a voltagelevel that remains substantially constant relative to a temperatureassociated with the bandgap temperature sensor.
 2. The device of claim1, where the system controller is operable to determine a difference inthe base-emitter voltages, and to generate the bandgap reference voltagefrom the difference in the base-emitter voltages and at least one of thebase-emitter voltages.
 3. The device of claim 2, where the systemcontroller is operable to add the difference in the base-emittervoltages to one of the base-emitter voltages to generate the bandgapreference voltage.
 4. The device of claim 3, where the system controlleris operable to multiply the difference in the base-emitter voltages to aconstant value and then to add the multiplied difference in thebase-emitter voltages to one of the base-emitter voltages to generatethe bandgap reference voltage.
 5. The device of claim 4, where theconstant value is based at least in part on characteristics of thebandgap temperature sensor.
 6. The device of claim 1 where the bandgaptemperature sensor includes a variable current source to provide a firstcurrent to a transistor to generate a first base-emitter voltage signal,and to provide a second current to the transistor to generate a secondbase-emitter voltage signal.
 7. The device of claim 1 including ananalog-to-digital converter to convert base-emitter voltages intodigital base-emitter voltage signals, the system controller to generatethe bandgap voltage according to the digital base-emitter voltagesignals.
 8. A method comprising: detecting multiple base-emittervoltages generated by a bandgap temperature sensor; and generating abandgap reference voltage according to the multiple base-emitter voltagesignals, the bandgap reference voltage to remain substantially constantrelative to environmental temperature variations.
 9. The method of claim8, includes: determining a difference in the base-emitter voltages; andgenerating the bandgap reference voltage from the difference in thebase-emitter voltages and at least one of the base-emitter voltages. 10.The method of claim 9, where generating the bandgap reference voltageincludes adding the difference in the base-emitter voltages to one ofthe base-emitter voltages.
 11. The method of claim 10, re generating thebandgap reference voltage includes: multiplying the difference in thebase-emitter voltages to a constant value; and adding the multiplieddifference in the base-emitter voltages to one of the base-emittervoltages.
 12. The method of claim 11, where the constant value is basedat least in part on the characteristics of the bandgap temperaturesensor.
 13. The method of claim 8, includes: generating a firstbase-emitter voltage signal when a first current signal is provided to atransistor; generating a second base-emitter voltage signal when asecond current signal is provided to the transistor; determining adifference between the first base-emitter voltage signal and the secondbase-emitter voltage signal; and generating the bandgap referencevoltage based, at least in part, on the determined difference betweenthe first base-emitter voltage signal and the second base-emittervoltage signal.
 14. A system comprising: a memory to storecomputer-readable instructions; and a microprocessor to receive theinstructions stored in memory, the instructions, when executed, causethe microprocessor to: identify multiple base-emitter voltages generatedby a bandgap temperature sensor; and generate a bandgap referencevoltage according to the multiple base-emitter voltage signals, wherethe bandgap reference voltage having a voltage level that remainssubstantially constant relative to environmental temperature variations.15. The system of claim 14, where the microprocessor is operable todetermine a difference in the base-emitter voltages, and generate thebandgap reference voltage from the difference in the base-emittervoltages and at least one of the base-emitter voltages.
 16. The systemof claim 15 where the base-emitter voltages decrease as theenvironmental temperature increases, and the difference in thebase-emitter voltages increases as the environment temperatureincreases.
 17. The system of claim 15, where the microprocessor isoperable to add the difference in the base-emitter voltages to one ofthe base-emitter voltages to generate the bandgap reference voltage. 18.The system of claim 17, where the microprocessor is operable to multiplythe difference in the base-emitter voltages to a constant value, and addthe multiplied difference in the base-emitter voltages to one of thebase-emitter voltages to generate the bandgap reference voltage.
 19. Thesystem of claim 18, where the constant value is based at least in parton the characteristics of the bandgap temperature sensor.
 20. The systemof claim 14, where the bandgap temperature sensor is operable togenerate a first base-emitter voltage signal when a first current signalis provided to a transistor and to generate a second base-emittervoltage signal when a second current signal is provided to thetransistor; and where the microprocessor is operable to determine adifference between the first base-emitter voltage signal and the secondbase-emitter voltage signal, and generate the bandgap reference voltagebased, at least in part, on the determined difference between the firstbase-emitter voltage signal and the second base-emitter voltage signal.